1. Field of the Invention
The present invention relates to a standard-length positioning apparatus, and more particularly to a standard-length positioning apparatus suitable for use with an automated machine or the like which positions a continuous long material every predetermined dimension to process the same.
2. Description of the Prior Art
Generally, where a continuous long material is positioned every predetermined dimension to process the same as in a cutter, a printing machine, an automatic inserting machine and the like, a standard-length positioning apparatus adapted to stop the material every predetermined dimension is used.
The standard-length positioning apparatus of this kind most frequently used in the past is relied upon mark sensing. This apparatus is designed so that marks marked on the material every predetermined dimension are detected by a detector, for example, such as a photoelectric tube, a magnetic sensor or the like or a limit switch to stop a drive mechanism for feeding a material by the detection signal therefrom.
Recently, a digital positioning mechanism adapted to provide for positioning by a position feedback signal, without use of the above-described mark sensor, has been put into wide use.
However, any of these prior art apparatuses have inconveniences for use as a standard-length positioning apparatus. That is, in the former mark reading system, if, for example, reading error in mark should occur, the positioning would become impossible to carry out no stopping operation, resulting in feeding of exceeding materials. In addition, if patterns or scratches of the material other than marks are read, the stopping operation possibly takes place at a site not expected at all. Moreover, for example, if the machine is speeded up, the reading precision for marks has to be materially increased, which inevitably increases the cost, and there is a limitation in connection with the positioning precision including the increase in inertia moment of the machine resulting from the speed-up. In order that after detection of a mark, the drive mechanism is stopped by the detection signal, the mechanical strength of other parts including the drive mechanism should be made more rigid and there is a limitation in large-sized structure as well as speed-up structure.
On the other hand, where the latter digital positioning mechanism is used, extremely high speed positioning becomes possible since the detection of mark need not be required. However, the positioning takes place without confirmation of a position of the material, and therefore, there occurs an inconvenience where, for example, positioning of material having printed matter, patterns or the like or material for which strict precision is required takes place. This is because of the fact that uncalculatable primary factors of errors in slip, deformation, precision environmental conditions of machineries and/or materials cannot be ignored even if the position feedbark pulse is strictly set.
Furthermore, in view of the above-described problem, as a standard-length positioning apparatus which comprises a combination of a digital positioning and a mark sensing, a method as disclosed in Japanese patent Laid-Open No. 217,560/1984, for example, has been proposed. This apparatus comprises a first counter which counts pulses according to the amount of feed of material simultaneously with the start of the material and a second counter which counts predetermined time after marks marked on the material have been detected, whereby stop postioning is carried out by the output of the second counter. According to this structure, the stopping operation is basically carried out by detection of the mark, and therefore the positioning precision may be enhanced as compared with the control of digital positioning alone but tbe reading of mark is done during the high-speed operation, which the disadvantage with respect to the above-mentioned mark reading system remains unsolved. In addition, a further counter is necessary to be provided in addition to a normal counter, and therefore the control circuit becomes complicated to increase the cost. Moreover, in order that after reading the mark, a distance is set for proving a smooth falling, there involves a practical inconvenience in that the set value of the second counter cannot be made to a level below a predetermined value.
Incidentally, the mark reading system has a further significant problem in addition to the problems in terms of mechanism such as the responsiveness to speed-up, reading error and the like as described above. More specifically, where positioning of material having printed matter, patterns and the like is carried out, when a printed matter is present between marks, it is not possible to discriminate the printing from the mark, as a consequence of which positioning becomes impossible. Moreover, the provision of marks for purpose of reading other than the designed printing and patterns on the material as described is very conspicuous in case of material having a specific design, and involves an inconvenience in that the visual aesthetics is impaired.
As mentioned above, the conventional standard-length positioning apparatus has problems in view of malfunction, speed-up operation and the like.